Data exchange protocols (generally named protocols), represent a set of formal rules which describe how data can be transferred, particularly within networks. Thus protocols which occupy themselves with monitoring electrical and physical standards, arrangement of bits and bytes, as well as the transmission, establishment of errors and definition of the correction of a bit current, are defined as so-called "low-level" protocols. "High-level" protocols occupy themselves with formatting the data including the syntax of the signals, dialogue between terminal and computer, character sets, the sequence control system of signals, etc.
A protocol converter consists of a device or a programme which serves the same purposes, between translating different, non-identical protocols. Thus data structures of a protocol A are converted in a corresponding data structure into the other protocol B. Especially in computer systems, the data are thereby transported over bus lines.
The increasing processing speeds of computer systems resulting in the necessity of improvement of data transmission to peripheral equipment, sets high requirements to the protocol converter, which has to be incorporated in the data circuit between computer system and peripherals. Problems then arise if available slow input-/output (I/O)-systems must be adapted to newly developed, optimized, faster bus systems.
This generally occurs by means of special semi-conductor modules, so-called Bridge-Chips, which undertake the conversion of a slow protocol A into the fast protocol B.
In order to make certain that the newly developed protocol converters also function free of faults, it is necessary to test them before actual use, and if necessary rectify any defects and imperfections thus arising. Normally for this purpose, a test run is undertaken with a test software, in order to determine whether the new converter translates all data correctly. The data in the faster protocol B must therefore be generated (Bringup) from the conventional I/O test data. A protocol partner for the fast protocol B is therefore necessary (Bringup-Adapter), which prepares the test data for the new converter. For example, this can be a new faster computer system.
From the purpose of inserting the converter it arises that specified commands go in the one transmission direction (e.g. from the memory to the peripheral equipment) and are meaningful, but however not in the reverse direction. On this account, selection means are provided in many protocol converters to ensure that such commands which run in the "wrong" direction, are additionally suppressed, in order to guarantee a higher operational safety. This results in an intentionally implemented asymmetry in the protocol conversion between both protocols.
Typically, a test of the converter is first carried out, if the complete new system is ready for operation, and only then can the new chips be tested inside their normal ready for operation environment. If the complete system is however not yet available, the new converter should be tested independently of the corresponding system, and thus, as has already been indicated above, an external Bringup Adapter is required for the test data.
A possibility of achieving such a Bringup, is the design of a special environment by specially developed test environment chips which generate the test data of new faster protocols. This however has the disadvantage that additional chips must be manufactured, giving rise to correspondingly higher costs.
Another possibility exists in reconstructing the Bridge-Chip with primitive, slow and free-programmable logic modules, in order then to test them with the corresponding test programmes. This method is however costly. In addition, the primitive Bridge-Chip is slow, so that on this account, no kind of test can be carried out at the original speed.
A further possibility of testing an already designed protocol converter, consists of a software simulation of the converter for use to test the correct functionality. The preparation of such a simulation is already mainly necessary for the development process of the chip. Test data in the one protocol is fed in for testing the simulation protocol. The simulation protocol translates this output data into the second protocol, and the data thus resulting can be checked for its correctness.